Tuning the crystallite size of monoclinic ZrO_(2) to reveal critical roles of surface defects on m–ZrO_(2) catalyst for direct synthesis of isobutene from syngas

The effects of crystallite size on the physicochemical properties and surface defects of pure monoclinic ZrO_(2) catalysts for isobutene synthesis were studied.We prepared a series of monoclinic ZrO_(2) catalysts with different crystallite size by changing calcination temperature and evaluated their catalytic performance for isobutene synthesis from syngas.ZrO_(2) with small crystalline size showed higher CO conversion and isobutene selectivity,while samples with large crystalline size preferred to form dimethyl ether(DME)instead of hydrocarbons,much less to isobutene.Oxygen defects(ODefects)analyzed by X-ray photoelectron spectroscopy(XPS)provided evidence that more ODefectsoccupied on the surface of ZrO_(2) catalysts with smaller crystalline size.Electron paramagnetic resonance(EPR)and ultraviolet–visible diffuse reflectance(UV–vis DRS)confirmed the presence of high concentration of surface defects and Zr3+on mZrO_(2)-5.9 sample,respectively.In situ diffuse reflectance infrared Fourier transform spectroscopy(in situ DRIFTS)analysis indicated that the adsorption strength of formed formate species on catalyst reduced as the crystalline size decreased.These results suggested that surface defects were responsible for CO activation and further influenced the adsorption strength of surface species,and thus the products distribution changed.This study provides an in-depth insight for active sites regulation of ZrO_(2) catalyst in CO hydrogenation reaction.

Alkylation of Isobutane and Isobutene in Acidic Polyether Ionic Liquids

The Br?nsted-acidic polyether ionic liquids(ILs)with different polymerization degrees(n value)were prepared via the reaction of tetramethylguanidine and epoxy ethane,followed by successive reactions with 1,3-propane sultone and trifluoromethanesulfonic acid(TfOH).The prepared ILs were characterized by infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy,and their thermal stability was determined by thermal gravimetry.The synthesized polyether ILs coupled with TfOH were used to catalyze the alkylation reaction of isobutane and isobutene for the preparation of alkylate gasoline.The polyether ILs could improve the substrate dissolution and promote the separation of the catalyst from the products.The ideal IL(n=94)was determined.The optimized alkylation reaction conditions covered:a VTfOH/VIL ratio of 0.35,a reaction temperature of 40℃,a reaction time of 50 min,and a stirring speed of 800 r/min.The conversion of isobutene was 92.4%and the selectivity for the C8-product was 81.6%.Under optimal conditions,the catalyst life was determined and TfOH showed improved cyclic performance in the polyether ILs.After 8 operating cycles,the catalytic activity of the catalyst showed negligible decline.

Influence of Geometric Structure of Immobilized Aluminium Chloride Catalyst on Catalytic Property in Isobutene Polymerization

The catalytic property of AICl(3) catalyst immobilized on gamma -Al2O3 for isobutene polymerization has been studied. It was found that the activity, selectivity and stability of the catalyst are dependent greatly on geometric characteristic pf the pore structure and size of catalyst. Although the activity and selectivity of the catalysts with micro- and meso-pore structure are all high in initial stage, but their stability is low, while those with bimodal meso- and macro-pore structure are excellent. Increasing granularity of the catalyst(particle become fine) brings about an increase in isobutene conversion, but a decrease in selectivity, resulting in lower average molecular weight and iis broader distribution.

Selective Oxidation of Isobutene over CsFeCoBiMnMoO_x Mixed Oxide Catalyst

Mixed oxide catalyst Cs0.1Fe2Co6BiMnMo12Ox was prepared by the coprecipitation method. Selective oxidation of isobutene was carried out in a fixed-bed reactor over Cs0.1Fe2Co6BiMnMo12Ox. The results showed that the catalyst had high catalytic activity. Under the optimum reaction conditions (n(i-C4=):n(O2)=1:2-1:4, space velocity=180 h-1, T=360℃), the yields of methacrolein and methacrylic acid can reach 80% and 8%, respectively. The total yield of liquid products (methacrolein, methacrylic acid and acetic acid) can reach about 90%.

Promoting di-isobutene selectivity over ZnO/ZrO_(2)-SO_(4) in isobutene oligomerization

Isooctane attracts great interest in recent years because of its promising potential as friendlyenvironmental gasoline,which is obtained by dimerization of isobutene with a hydrogenation step.Herein,a solid acid catalyst sulfated zirconia modified by ZnO was prepared.The oligomerization of isobutene had been investigated over ZrO_(2)-SO_(4) and ZnO(X)/ZrO_(2)-SO_(4) catalyst in order to find efficient catalysts for the production of isobutene oligomers.The presence of ZnO obviously enhanced the dimerization of isobutene and ZnO(X)/ZrO_(2)-SO_(4) exhibited the highest di-isobutene yield of 60%.Kinetic studies showed the higher trimerization-to-dimerization activation energy ratios of ZnO(X)/ZrO_(2)-SO_(4) than those of ZrO_(2)-SO_(4) from 353 to 393 K.In addition,reaction rate of dimerization was higher than trimerization over ZnO(X)/ZrO_(2)-SO_(4).The high L/B ratio manifested the capability to enhance the selectivity of C8 in isobutene dimerization.Furthermore,ZnO(X)/ZrO_(2)-SO_(4) exhibited stable conversion for the dimerization of isobutene.

A-Site Effect on the Conversion of Bio-Ethanol into Isobutene over Ternary A1ZnyZrzOn Catalysts

Ternary multifunctional A1ZnyZrzOn catalysts are prepared by introducing A-site transition metals with the redox capability into binary Zn1Zr8On. Structure and morphology were investigated by means of XRD, BET and FESEM, respectively. Activity data showed that Cr addition exhibited obvious beneficial effect to promote isobutene production from direct conversion of bio-ethanol compared to other A-site metal dopants. A significant higher yield of isobutene over Cr-promoted Zn1Zr8On catalyst was also observed with respect to its binary Zn1Zr8On counterpart. The choice of A-site metal is of prime importance in the isobutene production, catalyzing mainly the ethanol dehydrogenation, meanwhile the appropriate addition of zinc on the catalyst surface is also essential for good isobutene yield.

Catalytic behavior of Mo-Bi-Fe-Co-K-M-O(M=Ce,Gd,CeGd)catalysts for selective oxidation of isobutene

The further improvement of methacrolein(MAL)selectivity from isobutene(IB)oxidation is crucial and challenging.In this study,based on the typical Mo-Bi-Fe-Co-K-O mixed metal oxide,the rare earth element Gd-doped,Ce-doped and CeGd co-doped catalysts were prepared by co-precipitation strategy to increase the selectivity of MAL from 47.9%to 49.8%,64.2% and 68.6%,respectively.In order to elucidate in-depth the promoting effect of Ce and/or Gd,various characterizations were utilized including X-ray diffraction patterns(XRD),Raman,X-ray fluorescence spectrometry(XRF),X-ray photoelectron spectroscopy(XPS),O_(2)-temperature programmed desorption(O_(2)-TPD),H2-temperature programmed reduction(H2-TPR),CO_(2)-temperature programmed desorption(CO_(2)-TPD),IB-temperature programmed desorption(i-C4-TPD)and in-situ IB-Fourier transform infrared spectroscopy(IB-FTIR).Both Ce and Gd finely regulate the bulk and surface structure of the catalyst,thus altering the redox ability,oxygen mobility and storage ability and basicity.Compared with Ce,Gd addition slightly regulates the variation of Co^(2+)/Co^(3+)redox couples,greatly enhances the interaction among the components on the catalyst,thus only increases the content of surface oxygen species and has little effect on their mobility.While Cecontaining catalyst performs stronger oxygen storage and migration ability,thus leading to the overproduction of surface Odefectspecies,which are proposed to be the active sites for the production of MAL and COx.The CeGd co-doped catalyst possesses the proper content of surface Odefectspecies,thus exhibits much higher MAL selectivity.Moreover,the promoting mechanism of Ce and/or Gd over IB oxidation is proposed.Therefore,this work is helpful for understanding the influence of rare earth elements on the structure of mixed metal oxides and the olefin selective oxidation reaction.

Adsorption of Isobutene on NanZSM-5 Type Zeolite with Various Si/Al Ratios： Molecular Simulation Study

Frameworks of NanZSM-5 type zeolites with various Si/A1 ratios have been constructed and optimized with molecular dynamic quench simulation. The results show that the structure parameters of NanZSM-5 type zeolite, including the bond length and atomic charges, are consistent with those predicted by ab initio cluster calculations. It was also observed that atomic charges of Si atoms were shifted to higher field in NanZSM-5 type zeolite with lower Si/Al ratio. Then, the adsorption of isobutene on NanZSM-5 with various Si/Al ratios has been investigated using grand canonical ensemble Monte Carlo simulation and Cvff-300-1.01 forcefield. The simulated adsorption amount was in good agreement with the experimental data. Based on these facts, the effects of Si/Al ratio on the adsorption amount and adsorption isotherms of isobutene on NanZSM-5 were predicted. The results indicated that Si/Al ratio was important for the adsorption of isobutene and the adsorption amount was decreased as the Si/Al ratio was increased, which can be explained that the atomic charge of Na^＋ cation would influence greatly the π electrons of the isobutene double bond due to the Coulomb force. In addition, the adsorption sites of isobutene and interaction energy of isobutene with NanZSM-5 were also discussed.

A Novel Catalyst for Isobutene Oligomerization to High Quality Gasoline

Dimerization of isobutene in liquid state to form high octane value gasoline components was investigated over a homemade novel ion exchange resin, SPPESK, which shows high activity and selectivity in isobutene dimerization under mild conditions.

Predicting of Covalent Organic Frameworks for Membrane-based Isobutene/1,3-Butadiene Separation:Combining Molecular Simulation and Machine Learning

Efficient separation of C4 olefins is of critical importance and a challenging task in petrochemical industry. Covalent organic frameworks(COFs) could be used as promising candidates for membrane-based isobutene/1,3-butadiene(i-C4H8/C4H6) separation. Owing to large amounts of COFs appearing, however, the rapid prediction of optimal COFs is imperative before experimental efforts. In this work, we combine molecular simulation and machine learning to study COF membranes for efficient isolation of i-C4H8 over C4H6. Using molecular simulation, four potential COF membranes, which possess both high membrane performance score (MPS) value and moderate membrane selectivity were screened out and the mechanism of membrane separation further revealed is an adsorption dominated process. Further, random forest(RF) model with high prediction accuracy(R2>0.84) was obtained and used for elucidating key factors in controlling the membrane selectivity and i-C4H8 permeability. Ultimately, the optimal COF features were obtained through structure-performance relationship study. Our results may trigger experimental efforts to accelerate the design of novel COFs with better i-C4H8/C4H6separation performance.

Spectroscopic analysis of acetamide-AlCl_(3)-based ionic liquid analog and their catalytic performance in isobutene oligomerization

The spectral structures of acetamide-AlCl_(3)-based ionic liquid(IL)analogs were determined in detail through IR,NMR,and Raman spectroscopy.IR spectroscopy showed that 0.65AA-1.0AlCl_(3) was the coordination structure of Al and O atoms because of the resonance structure of acetamide.The mutual verification of the results of ^(27)Al NMR and ^(1)H NMR indicated that acetamide coexisted mainly in the form of cationic Al species and molecular Al species in xAA-1.0AlCl_(3),and AA/AlCl_(3) molar ratio affected the transformation of cationic Al species to molecular Al species.xAA-1.0AlCl_(3) was used as a green acidic catalyst for isobutene oligomerization,and the effects of AA/AlCl_(3) molar ratio,reaction temperature,reaction time,and volumetric ratio between IL analog and isobutene on product distribution were investigated.Optimal reaction conditions were AA/AlCl_(3) molar ratio of 0.75,reaction temperature of 60 C,reaction time of 30 min,and catalyst/i-C4¼volumetric ratio of 1.4 v/v.Under optimal conditions,isobutene conversion,(C8^(-)+C12^(-))selectivity,(C16^(-)+C20^(-))selectivity,and by-product selectivity were 85.26,80.20,6.80,and 13.00 wt%,respectively。

Effect of Bi promoter on the performances of selective oxidation of isobutane to methacrolein over MoVO/AlPO_4 catalysts

The effects of Bi on the catalytic performance of selective oxidation of isobutane to methacrolein over MoVO/AlPO4 catalyst were investigated by XRD, FT-Raman, XPS, UV-vis DRS techniques. The results show that the addition of Bi component into the MoVO/AlPO4 catalyst obviously improves the catalytic performance, and the selectivity to methacrolein can increase from 14.2% to 45.1% with the increase of Bi/V molar ratio from 0 to 1. Combining the characterization results with the reaction evaluation, it is concluded that the catalytic activities of the MoV0.3Bix/AlPO4 catalysts are related to the crystalline phase composition and the dispersion of molybdenum and vanadium oxides species in general, and also to the V5＋/V4＋ molar ratio on the surface in particular.

由杂多钼酸盐前驱体制备的氧化钼催化剂催化CO_2存在下的异丁烷脱氢(英文)

Molybdenum based oxide catalysts Mo-H,Mo-Fe,Mo-Ce,and Mo-Sn were prepared by calcining H3PMo12O40,Fe1.5 PMo 12O40,Ce1.5PMo12O40,and Sn1.5 PMo12O40 heteropolyanion precursors at700℃,respectively.The prepared oxides have been characterized and tested for the dehydrogenation of isobutane(IB)to isobutene in the presence of CO2.The effects of temperature,time on stream,and CO2 /IB ratio were investigated.It was found that α-and-MoO3 phases were present in all catalysts.Catalytic tests showed that increasing the reaction temperature increased both the conversion and isobutene selectivity,whereas increasing the CO2 /IB molar ratio increased the conversion but decreased the selectivity for isobutene.Iron was found to be an effective additive element for the enhancement of catalytic activity compared with Ce and Sn.

Novel Pt-Ni Bimetallic Catalysts Pt(Ni)-LaFeO_3/SiO_2 via Lattice Atomic-Confined Reduction for Highly Efficient Isobutane Dehydrogenation

In this study, a series of novel Pt-Ni bimetallic catalysts supported on LaFeO_3/SiO_2 with different amounts of Ni were prepared by the lattice atomic-confined reduction of LaFe_(1-x)(Ni, Pt)_xO_3/SiO_2 perovskite precursors and applied in isobutane dehydrogenation to isobutene reaction. The catalysts were characterized by X-ray diffraction, H_2-temperature-programmed reduction, Brunauer-Emmett-Teller analysis, transmission electron microscopy, energy dispersive X-ray, CO chemisorption, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The as-synthesized Pt-Ni bimetallic catalysts possessed smaller most probable particle size with tunable Pt-Ni interaction, depending on the Ni content. The catalyst with Ni content of 3.0 wt% showed excellent activity and stability(the isobutane conversion and isobutene selectivity remained at about 38% and 92%, respectively, after 310 min) for the isobutane dehydrogenation reaction. It also provided approximately six times turnover frequency of the catalyst without Ni. The excellent activity and stability of the 3.0 wt% Ni-containing catalyst can be attributed to its small metal nanoparticles with high dispersion and suitable Pt-Ni interaction. Moreover, the Pt(Ni)-LaFeO_3/SiO_2 catalyst with Ni content of 3.0 wt% had been run for more than 35 h without obvious loss of activity,indicating its long-term stability, and the decrease in the Pt-Ni interaction that accompanied the formation of the FeNi alloy phase was thought to be responsible for the slight decrease in activity.

Simple Preparation of Spherical Activated Carbon with Mesoporous Structure from Phenolic Resol and Associated Catalytic Performance in Isobutane Dehydrogenation

This study provides a detailed report on the synthesis of spherical activated carbon with mesoporous structure using a soluble low molecular weight phenolic resol precursor through an ammonium alginate assisted sol–gel method. The effects of calcinating temperature and the addition of CaCO_3 as a pore-enlarging agent on texture structure and catalytic performance in isobutane dehydrogenation to isobutene were investigated. Characterization of N_2 sorption,mechanical strength tests,and optical photographs confirmed that the obtained carbon materials had high mechanical strength,a good degree of sphericity,and a large surface area. Introducing CaCO_3 as a pore-enlarging agent during the preparation process promoted the formation of a mesoporous structure of carbon spheres and evidently increased the surface area and oxygen content,which can improve isobutane conversion and isobutene selectivity of these carbon spheres. The conversion of isobutane reached up to 28% for this spherical activated carbon,and the selectivity of isobutene reached up to 96%. Isobutane conversion increased with an increase in calcination temperature due to an increase in the oxygen content,whereas the selectivity of isobutene decreased due to the slight decrease in the specific surface area.

Kinetics of the Oxidative Dehydrogenation of Isobutane over Cr_2O_3/La_2(CO_3)_3

The oxidative dehydrogenation (ODH) of isobutane over Cr_2O_3/La_2(CO_3)_3 has been investigated in a low-pressure Knudsen cell reactor, under conditions where the kinetics of the primary reaction steps can be accurately determined. By heating the catalyst at a constant rate from 150-300℃, temperature fluctuations due to non-equilibrium adsorption are minimized. The evolved gas profiles show that ODH to isobutene and water is a primary reaction pathway, while carbon dioxide, which forms from the catalyst during reaction, is the only other product. This CO2 evolution may enhance the activity of the catalyst. Isobutene formation proceeds with the participation of lattice oxygen from the Cr2O3/La2(CO3)3 catalyst. The intrinsic Arrhenius rate constant for the ODH of isobutane isk(s-1) = 1011.5±2.2exp{-((55±5) -ΔHads kJmol-1)/RT}The small pre-exponential factor is expected for a concerted mechanism and for such a catalyst with a small surface area and limited porosity.

Effect of alcohol solvents treated ZrO(OH)_2 hydrogel on properties of ZrO_2 and its catalytic performance in isosynthesis

A series of ZrO2 catalysts were prepared by treating ZrO（OH）2 hydrogel with different alcohol solvents （C2-C4 alcohols） and calcining under N2 flow at 773 K for 3 h. The obtained ZrO2 catalysts were systematically characterized by the methods of N2 adsorption-desorption, powder X-ray diffraction, NH3 temperature-programmed desorption, and CO2 temperature-programmed desorption. The catalytic performance of each catalyst was evaluated in the selective synthesis of iso-C4 （isobutene and isobutane） and light olefins （C2-C4） from CO hydrogenation. The specific surface area increased for the ZrO2 catalysts obtained by treating ZrO（OH）2 hydrogel with different alcohol solvents. The amounts of both acidic and basic sites on the catalyst surface increased obviously. The catalytic activity （CO conversion） of ZrO2 catalysts also increased after the treatment with different alcohol solvents. The nighest activity was obtained over the catalyst which was pretreated with isopropanol. However, alcohol solvent treatment retarded the transformation of ZrO2 crystal structure from tetragonal phase to monoclinic phase, and subsequently resulted in the decrease of monoclinic phase in ZrO2, which led to the decrease of olefin selectivity in corresponding hydrocarbon products （C2-C4/CH）.

Catalytic Oxidative Dehydrogenation of Isobutane over KF-Zn3（PO4）2

KF Zn 3(PO 4) 2 catalyst was found to be effective for isobutane oxidative dehydrogenation into isobutene. The effects of O 2 concentration in feed gas on isobutene yield and selectivity were discussed. The modification of zinc phosphate by potassium fluoride leads to the formation of a new compound KF Zn 3(PO 4) 2 and surface basic sites, the catalytic performance of which is thus improved.

Mild and Highly Selective Preparation of Alkylate Gasoline Promoted by Using Polyetheramine-Based Acidic Ionic Liquid

A polyetheramine(PEA)-based Br?nsted-acidic ionic liquid(IL)was firstly prepared and used to promote the alkylation of isobutane with isobutene catalyzed by trifluoromethanesulfonic acid(TfOH).PEA-IL not only can resolve the persistent problem of poor solubility of the volatile and refractory reactants,but also can satisfactorily exhibit the separation of the catalyst from product oil for reuse.The PEA-IL/TfOH catalytic system with an adjustable acidity ensures a high alkylate selectivity.Under the conditions covering a VIL/VTfOH ratio of 10:3,a temperature of 25°C,and a reaction time of 25 min,the C8-product selectivity reaches 86.63%.The PEA-IL/TfOH catalyst can be reused 13 times without a decrease in the catalytic performance.After many operating cycles,the hydrophobic PEA-IL can be easily regenerated by simply adding water.This study provides a green,economic,and highly efficient method for producing high-octane alkylate gasoline.